I had a similar issue where my WaterBodyRiver dissapeared on a certain camera angle. Found this post when trying to find a solution for it. However, I fixed it on my own after experimenting a bit more.
For me, increasing the “Far Distance Mesh Extent” on WaterZone object fixed the issue. Hope this works for you as well!
Thanks. I added two zeros, and now it’s not flashing anymore. (I don’t know why, I never received notifications that someone had written something. I always have to keep checking. Sorry for the late reply)